Finding version of Oracle database should be easy. As written here: How can I confirm a database is Oracle & what version it is using SQL? it's one command:
select * from v$version;
However it seems to be not working on some specific versions of Oracle. My database throws following exception while executing the command:
[Error] Script lines: 1-1 -------------------------- ORA-00911: invalid character Script line 1, statement line 1, column 23
I use Aqua Data Studio 15.0.14 to connect with DBMS.
select * from v$version
go
Aqua Data Studio uses go or / as statement separator. You can change this behavior under File-> Options.